Use of traffic displays for general aviation approach spacing : a human factors study

Volpe National Transportation Systems Center, Technical Reference Center;Civil Aerospace Medical Institute2007PDFResearch PaperNadler, EricYost, A.Kendra, A. J.John A. Volpe National Transportation Systems Center (U.S.)United States. Office of Aerospace MedicineInformation display systemsAir traffic controlADS-B DisplaysCDTI DisplaysNavigation DisplaysHuman FactorsPsychologyApplied PsychologyDOT/FAA/AM-07/30A flight experiment was conducted to assess human factors issues associated with pilot use of traffic displays for approachspacing. Sixteen multi-engine rated pilots participated. Eight flew approaches in a twin-engine Piper Aztec originating inSanford, ME, and eight flew approaches in the same aircraft originating in Atlantic City, NJ. The spacing target was aCessna 206. The traffic display was either a Garmin International MX-20\u2122 (the \u201cBasic\u201d Cockpit Display of TrafficInformation, or CDTI) or an MX-20\u2122 modified with features to help the pilot monitor the closing rate, the range andground speed of the traffic-to-follow, and ownship ground speed (Range Monitor). Two other Equipment conditions wereBaseline and Autopilot. Pilots successfully used the displays to maintain the assigned spacing on visual and instrumentapproaches. The spacing deviations were significantly lower when using the displays during visual approaches than whenattempting to maintain spacing without a traffic display. The mean spacing deviation during the IFR approaches was lessthan 0.10 NM for all three equipment conditions (Basic CDTI, Range Monitor, Autopilot), and these mean spacingdeviations did not differ significantly. Range Monitor features appeared to particularly benefit the low-hour pilots. Whilethe traffic display reduced visual reacquisition times, this effect was only found with pilots whose displays showed additionaltraffic (not only the traffic-to-follow). In general, however, the additional traffic was associated with less time betweenfixations on the display and higher workload. Subjects appeared to have had difficulty identifying an optimal display rangethat would simultaneously provide traffic awareness and spacing task performance. The traffic display necessarily requiresvisual attention and reduces the attention available for scanning the instrument panel and on visual approaches, the outsideworld. For this reason, even if pilots assume responsibility for spacing when they temporarily lose visual contact with theassigned traffic-to-follow, they should notify ATC of the loss of visual contact so that controllers can assume responsibilityfor separation from other aircraft.119